Drilling wells for oil and gas exploration invariably produces waste material. The drilling process typically involves the use rotary drill bits that are lubricated by drilling fluids sometimes called mud. As the drill bit grinds downward through soil and rock formation, large amounts of ground-up materials called drill cuttings and drilling fluids are generated, requiring environmentally safe disposal.
Many methods exist for disposing drill waste. These include on-site disposal methods, off-site disposal methods, land-treatment methods and other alternatives. Two of the well known methods for disposing of water-based drilling waste off-site are “land spraying” and “land spraying while drilling”. In the present document, “land spraying”, and “land spraying while drilling”, may be referred to individually and collectively as “landspraying”. Under suitable conditions, drill waste can be safely and beneficially sprayed over agricultural land.
However, excessive amounts of drill waste disposed within a given area of land, may lead to undesirable environmental side effects. Not surprisingly, governments at provincial/state and federal levels have instituted strict regulations regarding drill waste disposal methods. Compliance with the regulations requires tight control over where the drill waste fluid is sprayed and the amount of fluid sprayed over a given area.
Care must be taken to avoid spraying on sensitive areas such as bodies of water, steep hills, bales of hay, physical structures and the like. In addition one attempts to limit the amount of waste deposited in any given unit of area to safe amounts. What is deemed safe can be based on the chemical properties of the waste fluid.
Current conventional methods require a technician to physically scout and review the land. The technician calculates the total land area required for disposal based on the volume and chemical properties of drill waste fluid. The technician assesses the suitability of the land by taking representative soil samples to establish baseline soil chemistry of zones to be sprayed. The technician excludes areas that have high slopes, bodies of water, and other zones made unsuitable for spraying by seasonal factors.
After the boundaries of zones to be sprayed are determined, the operator of a truck loaded with drill waste fluid, is provided with information regarding approved zones to be sprayed, and the excluded areas.
The operator of the truck must either visually inspect the land being sprayed, or remain in communication with a technician, to avoid spraying outside the approved marked zones. It should be noted that the technician is not on-site during the entirety of each spraying operation, and thus the operator of the truck is responsible for spraying only on approved zones.
Drilling mud is a difficult fluid to handle. Drill cuttings in the fluid make it difficult to exercise flow control, other than fully opening to allow fluid discharge or fully closing to disallow fluid discharge. Often, vacuum trucks or similarly equipped vehicles, are used for landspraying. After the vacuum system is pressurized, the spraying operation is started and stopped manually using a simple valve operated by the truck operator depending on the location of the truck relative to zones designated for spraying. After disposal, manual mapping of the sprayed areas is performed for reporting purposes to comply with regulations.
There are many problems with these current conventional practices. During winter months, the technician scouting the land is often hampered by snow and uses, at best, dated aerial photographs for assessment. Further, post spraying mapping may be impaired by rain, snow and agricultural activities, which may lead to inaccuracies in the reported data. Trucks that discharge the drill waste fluid have no engineered environmental safeguards in place to ensure regulatory compliance. Accordingly, the onus is on the truck operator to perform landspraying in a compliant manner, relying largely on visual inspection, during good or poor weather, daytime and night conditions. As the truck operator is often among the least trained persons with regard to regulatory compliance requirements, reliance on the operator entails a high risk of non-compliance as a result of human error, weather conditions, poor visibility and the like.
Systems and methods for dispensing fluids on agricultural land are known. U.S. Pat. No. 7,370,589 to Wilkerson et al. for example, discloses a fluid dispenser aimed at improving in-furrow chemical application. The dispenser is operable to dispense fluid at a second location, after detecting that an object has passed a first location. Such known systems however, are aimed at improving efficiency and do not provide adequate safeguards to avoid overlap of zones on which fluids are dispensed, and require physical marker objects to be present on the target surface prior to applying the fluid. The requirement for physical markings may be costly and may limit available candidate land surfaces for landspraying. Moreover, the operation of known systems and methods does not take the slope of the terrain into account, which is a limiting factor for suitability for landspraying.
Accordingly, a system and method is needed to overcome the deficiencies of the conventional landspraying methods for drill waste disposal namely to better manage compliance with regulations for controlled placement, concerning where sprayed and amount sprayed.